diff mbox

[RFC,v2] sched: reflect sched_entity movement into task_group's utilization

Message ID 1464080252-17209-1-git-send-email-vincent.guittot@linaro.org
State Superseded
Headers show

Commit Message

Vincent Guittot May 24, 2016, 8:57 a.m. UTC 
Ensure that the changes of the utilization of a sched_entity will be
reflected in the task_group hierarchy.

This patch tries another way than the flat utilization hierarchy proposal
to ensure the changes will be propagated down to the root cfs.

The way to compute the sched average metrics stays the same so the
utilization only need to be synced with the local cfs rq timestamp.

Changes since v1:
- This patch needs the patch that fixes issue with rq->leaf_cfs_rq_list
  "sched: fix hierarchical order in rq->leaf_cfs_rq_list" in order to work
  correctly. I haven't sent them as a single patchset because the fix is
  independant of this one
- Merge some functions that are always used together
- During update of blocked load, ensure that the sched_entity is synced
  with the cfs_rq applying changes
- Fix an issue when task changes its cpu affinity

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>

---
 kernel/sched/fair.c  | 168 ++++++++++++++++++++++++++++++++++++++++++++-------
 kernel/sched/sched.h |   1 +
 2 files changed, 147 insertions(+), 22 deletions(-)

-- 
1.9.1

Comments

Vincent Guittot June 1, 2016, 3:26 p.m. UTC | #1 
On 1 June 2016 at 15:36, Peter Zijlstra <peterz@infradead.org> wrote:
> On Tue, May 24, 2016 at 10:57:32AM +0200, Vincent Guittot wrote:

>

>> +/*

>> + * Save how much utilization has just been added/removed on cfs rq so we can

>> + * propagate it across the whole tg tree

>> + */

>> +static void set_tg_cfs_rq_util(struct cfs_rq *cfs_rq, int delta)

>> +{

>> +     if (cfs_rq->tg == &root_task_group)

>> +             return;

>> +

>> +     cfs_rq->diff_util_avg += delta;

>> +}

>

> function name doesn't really reflect its purpose..


ok, i will change it

>

>> +

>> +/* Take into account the change of the utilization of a child task group */

>

> This comment could be so much better... :-)


yes, i'm going to add more details of what is done

>

>> +static void update_tg_cfs_util(struct sched_entity *se, int blocked)

>> +{

>> +     int delta;

>> +     struct cfs_rq *cfs_rq;

>> +     long update_util_avg;

>> +     long last_update_time;

>> +     long old_util_avg;

>> +

>> +

>> +     /*

>> +      * update_blocked_average will call this function for root cfs_rq

>> +      * whose se is null. In this case just return

>> +      */

>> +     if (!se)

>> +             return;

>> +

>> +     if (entity_is_task(se))

>> +             return 0;

>> +

>> +     /* Get sched_entity of cfs rq */

>> +     cfs_rq = group_cfs_rq(se);

>> +

>> +     update_util_avg = cfs_rq->diff_util_avg;

>> +

>> +     if (!update_util_avg)

>> +             return 0;

>> +

>> +     /* Clear pending changes */

>> +     cfs_rq->diff_util_avg = 0;

>> +

>> +     /* Add changes in sched_entity utilizaton */

>> +     old_util_avg = se->avg.util_avg;

>> +     se->avg.util_avg = max_t(long, se->avg.util_avg + update_util_avg, 0);

>> +     se->avg.util_sum = se->avg.util_avg * LOAD_AVG_MAX;

>> +

>> +     /* Get parent cfs_rq */

>> +     cfs_rq = cfs_rq_of(se);

>> +

>> +     if (blocked) {

>> +             /*

>> +              * blocked utilization has to be synchronized with its parent

>> +              * cfs_rq's timestamp

>> +              */

>> +             last_update_time = cfs_rq_last_update_time(cfs_rq);

>> +

>> +             __update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)),

>> +                       &se->avg,

>> +                       se->on_rq * scale_load_down(se->load.weight),

>> +                       cfs_rq->curr == se, NULL);

>> +     }

>> +

>> +     delta = se->avg.util_avg - old_util_avg;

>> +

>> +     cfs_rq->avg.util_avg =  max_t(long, cfs_rq->avg.util_avg + delta, 0);

>> +     cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * LOAD_AVG_MAX;

>> +

>> +     set_tg_cfs_rq_util(cfs_rq, delta);

>> +}

>

> So if I read this right it computes the utilization delta for group se's

> and propagates it into the corresponding parent group cfs_rq ?


yes

>

>> @@ -6276,6 +6368,8 @@ static void update_blocked_averages(int cpu)

>>

>>               if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, true))

>>                       update_tg_load_avg(cfs_rq, 0);

>> +             /* Propagate pending util changes to the parent */

>> +             update_tg_cfs_util(cfs_rq->tg->se[cpu], true);

>

> And this is why you need the strict bottom-up thing fixed..


yes

>

>> @@ -8370,6 +8464,20 @@ static void detach_task_cfs_rq(struct task_struct *p)

>>

>>       /* Catch up with the cfs_rq and remove our load when we leave */

>>       detach_entity_load_avg(cfs_rq, se);

>> +

>> +     /*

>> +      * Propagate the detach across the tg tree to ake it visible to the

>> +      * root

>> +      */

>> +     for_each_sched_entity(se) {

>> +             cfs_rq = cfs_rq_of(se);

>> +

>> +             if (cfs_rq_throttled(cfs_rq))

>> +                     break;

>> +

>> +             update_load_avg(se, 1);

>> +             update_tg_cfs_util(se, false);

>> +     }

>>  }

>>

>>  static void attach_task_cfs_rq(struct task_struct *p)

>> @@ -8399,8 +8507,21 @@ static void switched_from_fair(struct rq *rq, struct task_struct *p)

>>

>>  static void switched_to_fair(struct rq *rq, struct task_struct *p)

>>  {

>> +     struct sched_entity *se = &p->se;

>> +     struct cfs_rq *cfs_rq;

>> +

>>       attach_task_cfs_rq(p);

>>

>> +     for_each_sched_entity(se) {

>> +             cfs_rq = cfs_rq_of(se);

>> +

>> +             if (cfs_rq_throttled(cfs_rq))

>> +                     break;

>> +

>> +             update_load_avg(se, 1);

>> +             update_tg_cfs_util(se, false);

>> +     }

>> +

>>       if (task_on_rq_queued(p)) {

>>               /*

>>                * We were most likely switched from sched_rt, so

>

> So I would expect this to be in attach_task_cfs_rq() to mirror the

> detach_task_cfs_rq().


yes. My goal what to rely on the enqueue to the propagate the move
during a task_move_group but it's better to place it in
attach_task_cfs_rq so we have same sequence for attaching and
detaching

>

> Also, this change is somewhat independent but required for the 'flat'

> util measure, right?


don't know if it's needed for flat util measure as the main interest
of flat util measure is to not go through the tg tree
Dietmar Eggemann June 1, 2016, 7:45 p.m. UTC | #2 
On 01/06/16 13:54, Peter Zijlstra wrote:
> On Tue, May 24, 2016 at 10:57:32AM +0200, Vincent Guittot wrote:

>> Ensure that the changes of the utilization of a sched_entity will be

>> reflected in the task_group hierarchy.

>>

>> This patch tries another way than the flat utilization hierarchy proposal

>> to ensure the changes will be propagated down to the root cfs.


IMHO, the 'flat utilization hierarchy' discussion started here:
https://lkml.org/lkml/2016/4/1/514

In the meantime I continued to play with the idea of a flat utilization
hierarchy based on the exiting PELT code. I just sent out the RFC patch
set for people to compare with Vincent's approach.

> Which would be:

> 

>  lkml.kernel.org/r/1460327765-18024-5-git-send-email-yuyang.du@intel.com

> 

> Right? Yuyang, there were some issues with the patches leading up to

> that proposal, were you going to update the flat util thing without

> those patches or can you find yourself in Vince's patches?


I think Yuyang dropped the 'flat utilization hierarchy' in
https://lkml.org/lkml/2016/4/28/270

> (just so I can get a picture of what all patches to look at when

> reviewing)
diff mbox

Patch

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 07f0f1b..2714e31 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2591,6 +2591,7 @@  static void update_cfs_shares(struct cfs_rq *cfs_rq)
 
 	reweight_entity(cfs_rq_of(se), se, shares);
 }
+
 #else /* CONFIG_FAIR_GROUP_SCHED */
 static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
 {
@@ -2817,6 +2818,28 @@  __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
 	return decayed;
 }
 
+#ifndef CONFIG_64BIT
+static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
+{
+	u64 last_update_time_copy;
+	u64 last_update_time;
+
+	do {
+		last_update_time_copy = cfs_rq->load_last_update_time_copy;
+		smp_rmb();
+		last_update_time = cfs_rq->avg.last_update_time;
+	} while (last_update_time != last_update_time_copy);
+
+	return last_update_time;
+}
+#else
+static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
+{
+	return cfs_rq->avg.last_update_time;
+}
+#endif
+
+
 #ifdef CONFIG_FAIR_GROUP_SCHED
 /*
  * Updating tg's load_avg is necessary before update_cfs_share (which is done)
@@ -2884,8 +2907,86 @@  void set_task_rq_fair(struct sched_entity *se,
 		se->avg.last_update_time = n_last_update_time;
 	}
 }
+
+/*
+ * Save how much utilization has just been added/removed on cfs rq so we can
+ * propagate it across the whole tg tree
+ */
+static void set_tg_cfs_rq_util(struct cfs_rq *cfs_rq, int delta)
+{
+	if (cfs_rq->tg == &root_task_group)
+		return;
+
+	cfs_rq->diff_util_avg += delta;
+}
+
+/* Take into account the change of the utilization of a child task group */
+static void update_tg_cfs_util(struct sched_entity *se, int blocked)
+{
+	int delta;
+	struct cfs_rq *cfs_rq;
+	long update_util_avg;
+	long last_update_time;
+	long old_util_avg;
+
+
+	/*
+	 * update_blocked_average will call this function for root cfs_rq
+	 * whose se is null. In this case just return
+	 */
+	if (!se)
+		return;
+
+	if (entity_is_task(se))
+		return 0;
+
+	/* Get sched_entity of cfs rq */
+	cfs_rq = group_cfs_rq(se);
+
+	update_util_avg = cfs_rq->diff_util_avg;
+
+	if (!update_util_avg)
+		return 0;
+
+	/* Clear pending changes */
+	cfs_rq->diff_util_avg = 0;
+
+	/* Add changes in sched_entity utilizaton */
+	old_util_avg = se->avg.util_avg;
+	se->avg.util_avg = max_t(long, se->avg.util_avg + update_util_avg, 0);
+	se->avg.util_sum = se->avg.util_avg * LOAD_AVG_MAX;
+
+	/* Get parent cfs_rq */
+	cfs_rq = cfs_rq_of(se);
+
+	if (blocked) {
+		/*
+		 * blocked utilization has to be synchronized with its parent
+		 * cfs_rq's timestamp
+		 */
+		last_update_time = cfs_rq_last_update_time(cfs_rq);
+
+		__update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)),
+			  &se->avg,
+			  se->on_rq * scale_load_down(se->load.weight),
+			  cfs_rq->curr == se, NULL);
+	}
+
+	delta = se->avg.util_avg - old_util_avg;
+
+	cfs_rq->avg.util_avg =  max_t(long, cfs_rq->avg.util_avg + delta, 0);
+	cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * LOAD_AVG_MAX;
+
+	set_tg_cfs_rq_util(cfs_rq, delta);
+}
+
 #else /* CONFIG_FAIR_GROUP_SCHED */
 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
+
+static inline void set_tg_cfs_rq_util(struct cfs_rq *cfs_rq, int delta) {}
+
+static inline void update_tg_cfs_util(struct sched_entity *se, int sync) {}
+
 #endif /* CONFIG_FAIR_GROUP_SCHED */
 
 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
@@ -2925,6 +3026,7 @@  update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq)
 {
 	struct sched_avg *sa = &cfs_rq->avg;
 	int decayed, removed_load = 0, removed_util = 0;
+	int old_util_avg = sa->util_avg;
 
 	if (atomic_long_read(&cfs_rq->removed_load_avg)) {
 		s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
@@ -2947,6 +3049,8 @@  update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq)
 	smp_wmb();
 	cfs_rq->load_last_update_time_copy = sa->last_update_time;
 #endif
+	if (removed_util)
+		set_tg_cfs_rq_util(cfs_rq, sa->util_avg - old_util_avg);
 
 	if (update_freq && (decayed || removed_util))
 		cfs_rq_util_change(cfs_rq);
@@ -3000,6 +3104,8 @@  static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s
 	cfs_rq->avg.util_avg += se->avg.util_avg;
 	cfs_rq->avg.util_sum += se->avg.util_sum;
 
+	set_tg_cfs_rq_util(cfs_rq, se->avg.util_avg);
+
 	cfs_rq_util_change(cfs_rq);
 }
 
@@ -3008,12 +3114,13 @@  static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s
 	__update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
 			  &se->avg, se->on_rq * scale_load_down(se->load.weight),
 			  cfs_rq->curr == se, NULL);
-
 	cfs_rq->avg.load_avg = max_t(long, cfs_rq->avg.load_avg - se->avg.load_avg, 0);
 	cfs_rq->avg.load_sum = max_t(s64,  cfs_rq->avg.load_sum - se->avg.load_sum, 0);
 	cfs_rq->avg.util_avg = max_t(long, cfs_rq->avg.util_avg - se->avg.util_avg, 0);
 	cfs_rq->avg.util_sum = max_t(s32,  cfs_rq->avg.util_sum - se->avg.util_sum, 0);
 
+	set_tg_cfs_rq_util(cfs_rq, -se->avg.util_avg);
+
 	cfs_rq_util_change(cfs_rq);
 }
 
@@ -3056,27 +3163,6 @@  dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
 		max_t(s64,  cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
 }
 
-#ifndef CONFIG_64BIT
-static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
-{
-	u64 last_update_time_copy;
-	u64 last_update_time;
-
-	do {
-		last_update_time_copy = cfs_rq->load_last_update_time_copy;
-		smp_rmb();
-		last_update_time = cfs_rq->avg.last_update_time;
-	} while (last_update_time != last_update_time_copy);
-
-	return last_update_time;
-}
-#else
-static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
-{
-	return cfs_rq->avg.last_update_time;
-}
-#endif
-
 /*
  * Task first catches up with cfs_rq, and then subtract
  * itself from the cfs_rq (task must be off the queue now).
@@ -3287,6 +3373,7 @@  enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 	enqueue_entity_load_avg(cfs_rq, se);
 	account_entity_enqueue(cfs_rq, se);
 	update_cfs_shares(cfs_rq);
+	update_tg_cfs_util(se, false);
 
 	if (flags & ENQUEUE_WAKEUP) {
 		place_entity(cfs_rq, se, 0);
@@ -3388,6 +3475,8 @@  dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 
 	update_min_vruntime(cfs_rq);
 	update_cfs_shares(cfs_rq);
+	update_tg_cfs_util(se, false);
+
 }
 
 /*
@@ -3565,6 +3654,7 @@  entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
 	 */
 	update_load_avg(curr, 1);
 	update_cfs_shares(cfs_rq);
+	update_tg_cfs_util(curr, false);
 
 #ifdef CONFIG_SCHED_HRTICK
 	/*
@@ -4438,6 +4528,7 @@  enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 
 		update_load_avg(se, 1);
 		update_cfs_shares(cfs_rq);
+		update_tg_cfs_util(se, false);
 	}
 
 	if (!se)
@@ -4498,6 +4589,7 @@  static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 
 		update_load_avg(se, 1);
 		update_cfs_shares(cfs_rq);
+		update_tg_cfs_util(se, false);
 	}
 
 	if (!se)
@@ -6276,6 +6368,8 @@  static void update_blocked_averages(int cpu)
 
 		if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, true))
 			update_tg_load_avg(cfs_rq, 0);
+		/* Propagate pending util changes to the parent */
+		update_tg_cfs_util(cfs_rq->tg->se[cpu], true);
 	}
 	raw_spin_unlock_irqrestore(&rq->lock, flags);
 }
@@ -8370,6 +8464,20 @@  static void detach_task_cfs_rq(struct task_struct *p)
 
 	/* Catch up with the cfs_rq and remove our load when we leave */
 	detach_entity_load_avg(cfs_rq, se);
+
+	/*
+	 * Propagate the detach across the tg tree to ake it visible to the
+	 * root
+	 */
+	for_each_sched_entity(se) {
+		cfs_rq = cfs_rq_of(se);
+
+		if (cfs_rq_throttled(cfs_rq))
+			break;
+
+		update_load_avg(se, 1);
+		update_tg_cfs_util(se, false);
+	}
 }
 
 static void attach_task_cfs_rq(struct task_struct *p)
@@ -8399,8 +8507,21 @@  static void switched_from_fair(struct rq *rq, struct task_struct *p)
 
 static void switched_to_fair(struct rq *rq, struct task_struct *p)
 {
+	struct sched_entity *se = &p->se;
+	struct cfs_rq *cfs_rq;
+
 	attach_task_cfs_rq(p);
 
+	for_each_sched_entity(se) {
+		cfs_rq = cfs_rq_of(se);
+
+		if (cfs_rq_throttled(cfs_rq))
+			break;
+
+		update_load_avg(se, 1);
+		update_tg_cfs_util(se, false);
+	}
+
 	if (task_on_rq_queued(p)) {
 		/*
 		 * We were most likely switched from sched_rt, so
@@ -8443,6 +8564,9 @@  void init_cfs_rq(struct cfs_rq *cfs_rq)
 	atomic_long_set(&cfs_rq->removed_load_avg, 0);
 	atomic_long_set(&cfs_rq->removed_util_avg, 0);
 #endif
+#ifdef CONFIG_FAIR_GROUP_SCHED
+	cfs_rq->diff_util_avg = 0;
+#endif
 }
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 9693fe9..808d1b1 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -389,6 +389,7 @@  struct cfs_rq {
 	unsigned long runnable_load_avg;
 #ifdef CONFIG_FAIR_GROUP_SCHED
 	unsigned long tg_load_avg_contrib;
+	long diff_util_avg;
 #endif
 	atomic_long_t removed_load_avg, removed_util_avg;
 #ifndef CONFIG_64BIT